1. Field of the Invention
This invention relates to an apparatus for withdrawing blood from a vein and simultaneously filling multiple collection tubes. The apparatus includes a movable sheath which protects the technician from inadvertently contacting the withdrawn needle after use and a laminar flow transition chamber between the blood withdrawal needle and the multiple collection tubes.
2. Discussion of the Prior Art
The withdrawal of blood from a vein for the purpose of analysis is customarily done by inserting one end of a double ended hollow needle into a vein and inserting an evacuated collection tube onto the septum protected other end. Analytical laboratory practice dictates that multiple sample tubes be used where more than one test is to be run. The filling of multiple sample tubes is done serially, as one tube fills, it is withdrawn from the double ended needle and another sample tube is inserted onto the septum protected end of the needle. Since even the most common place blood analysis requires that multiple sample tubes be filled, it is the exception where a single tube is filled.
While it is obvious that the serial filling of the sample tube is slower than simultaneous filling of multiple tubes, there are other, more subtle, problems associated with the serial operation. The withdrawal needle must be centrally positioned within the patient's vein to avoid the rupture and destruction of red blood cells due to high velocity contact between the needle and the interior wall of the vein. This can render the blood sample worthless. The difficulty of holding the needle in the proper position is substantially increased when the technician is obliged to hold the assembly with one hand during the time the original sample tube is withdrawn and a new blood sample tube is inserted onto the septum protected end of the needle.
The danger associated with drawing blood samples from a patient is well recognized and certain safeguards have been adopted to protect the patient and the technician who performs the phlebotomy. While single-use sterile needles are normally effective to protect the patient from infectious diseases and reduce the danger to the technician, the needle is still exposed from the time it is withdrawn from the patient until it can be safely disposed of.
Despite the fact that current blood analysis instruments utilize only a small fraction of the quantity in the common sample tube, typically less than 1% of the volume within the tube, the difficulty of manipulating a much smaller tube during the serial filling of multiple tubes has presented a substantial obstacle to any reduction in size. While the actual amount of blood wasted due to the continued use of the large tube is relatively insignificant to the patient, the disposal of the unused blood presents a problem of ever increasing importance to the analytical laboratory for both cost and safety reasons.
The problems presented by a blood sample contaminated with ruptured red blood cells are well recognized and technicians are given training in the techniques which minimize such destruction. Nevertheless, it still occurs with sufficient frequency to be a concern. Even the most careful technician may be unable to prevent the high velocity impact of the blood against the sample tube during the initial phase of the filling procedure. Additionally, in the case where multiple samples are withdrawn from a patient with relatively small or constricted veins, the difficulty of holding the needle in a position away from the vein wall is such that additional sample must be drawn to ensure a sufficient number of samples uncontaminated by ruptured red blood cells.
The various tests performed on the withdrawn blood sample sometimes require that the blood be treated at the time it is withdrawn, for example, the addition of anticoagulants. Since these treatments render the blood unsuitable for other tests, each such treatment requires a discrete sample tube.
Various attempts have been made to solve individual problems discussed above. For example U.S. Pat. No. 4,492,634 discloses a sample collection tube which includes a baffle portion of the elastomeric stopper. The baffle is designed to curtail the potential mechanical hemolysis resulting from high velocity impact of the red blood cells against the wall of the sample tube during the initial inrush of blood.
The blood collection tube described in U.S. Pat. No. 4,434,802 includes a narrow bore primary tube which acts on the jet of bloodgushing from the needle by peripheral lateral attraction to convert the flow into a relatively slow and well controlled flow to reduce the damage caused to red blood cells.
The teaching of U.S. Pat. No. 4,947,863 is directed to protection against accidental needle stick from the collection needle. To this end, an outer sleeve is coaxially positioned over the blood collection tube holder and is adapted to slide over the collection needle.
U.S. Pat. No. 4,703,762 describes a blood sample withdrawing device which has the ability to fill two sample tubes, connected in tandem, from the same puncture. However, this device requires the use of specialized sample tubes which are not evacuated.
The multiple sample blood collection system shown in U.S. Pat. No. 3,933,439 does not allow the use of standard collection tubes but utilizes a highly specialized elastic bellows arrangement which accommodates the later withdrawal of individual samples.